1. Field of the Invention
The present invention relates to improvements in centrifugal extractors of the single-stage and multi-stage type and more particularly to the production of a system for recycling one or the other of the two liquids recovered after decantation
2. History of the Related Art
Reference may advantageously be made to Applicants' French Patents Nos. 1 541 754, 2 093 055, 2 255 958 and 2 417 324, concerning the general arrangement of centrifugal extractors of the type envisaged by the invention.
It will be noted that a single-stage centrifugal extractor includes a fixed vessel, inside which a decanter bowl is driven in rotation. The lower part of the bowl is constituted by a suction turbine which is possibly associated with an auxiliary agitator The turbine and the agitator are placed at the level of a mixing vat or chamber at the base of the fixed vessel. This vat comprises radial pipes opening outside the vessel for supplying the two liquids to be mixed.
The upper part of the vessel comprises two compartments for collecting the liquids separated in the bowl. These compartments communicate via outer orifices with the outside or with the inlet of an adjacent centrifugal extractor.
Two liquids of different densities (a heavy phase and a light phase) are introduced into the vat of the vessel and are intimately mixed. The mixture is then sucked inside the bowl in order to be separated therein under the action of centrifugal force. The two separated liquids are thus respectively discharged continuously in the compartments provided in the upper part of the vessel.
Furthermore, a multi-stage centrifugal extractor essentially comprises a common bowl mounted to rotate about its axis of symmetry, agitators carried by a shaft which is fixed or rotates about the same axis at a lower speed than that of the bowl, and, finally, deflectors forming baffles fixed on the bowl, thus defining therewith grooves or chambers with circular edges.
It is then ascertained that each of the mixing chambers is intercalated between two decantation chambers, and vice versa. Each decantation chamber comprises a spout for the light phase which opens out above the mixing chamber of the lower stage and a vertical channel for evacuating the heavy phase which opens out above the mixing chamber of the upper stage. This arrangement thus allows the heavy phase liquid and the light phase liquid to pass through the centrifugal extractor in opposite directions.
Such centrifugal extractors present certain drawbacks concerning the efficiency of the transfer of the solutes from one phase in the other. This drawback is especially due to the decantation effected subsequently, or to the flowrates of the two liquids which are too different.
It is a particular object of the present invention to overcome these drawbacks.